2014 exam 1

ENGR 121
Section______ Instructor:_____________ Name: ____________________________
Form#: 22
Allowed materials include calculator (without wireless capability), pencil or pen.
Honor Statement: On my honor, I promise that I have not received any outside assistance on this exam (I didn’t look at another
student’s paper, I didn’t view any unauthorized written materials, I didn’t talk or listen to another student, . . .).
1 2 1 0 1
___________________________________________signature
also fill in CWID, name and course (121) . . . don’t forget to black in bubbles
you must show your work on problems that require calculations to receive credit
Problem 1
What type of relay is shown?
a.
b.
c.
d.
e.
f.
SPST
DPST
SPDT
DPDT
ABC
ABC one coil
Problem 2
Which is true of a 3-way valve?
a. Allows 3 separate water sources to be turned on or off independently
b. Allows a single source to be diverted down any one of three outlets
c.
Allows a single source to be diverted to three outlets at the same time
d. Allows a single source to be diverted to either of two outlets
e. Allows a single source to be diverted to two outlets at the same time
Problem 3
In the fishtank system, what is the purpose of the relays?
a. Use a small current to control the flow of a larger current
b. Use a 5V system to control a 12V device
c.
Use a large current to control the flow of a smaller current
d. Use a 12V system to control a 5V device
e. Work magic
f.
Frustrate students
g. a and b
h. c and d
Problem 4
Which leg of a transistor is designed to receive a small current in order to control larger
current flow between the other two legs?
a.
b.
c.
d.
e.
f.
g.
h.
i.
Collector
Base
Emitter
Microcontroller
Receiver
Jackleg
Pant leg
Last leg
Lego
Problem 5
What is the purpose of a flyback diode?
a. To act as a cooling system so that an electromagnetic device does not overheat
b. To generate power to operate a circuit without being plugged into the wall
c.
To dissipate energy constantly during operation of an electromagnetic device
d. To dissipate energy immediately after an electromagnetic device is switched off
e. To provide a “short circuit” so that power never enters an electromagnetic device
Problem 6
For the electrical symbol shown, which configuration will result in current flow?
a. Positive on the right, negative on the left
b. Positive on the left, negative on the right
c.
Depends on other factors
d. a and b
e. None of the above
Problem 7
Assuming the power busses (two left-hand columns) of the breadboard are properly energized with
5V, which of the following circuits is correctly wired according to the circuit diagram?
A
C
B
D
Problem 8
What does UCL stand for?
a. Upper Calibration Level
b. Upper Conductivity Limit
c.
Upper Control Line
d. Upper Calibration Line
e. Upper Control Limit
f.
Upper Conductivity Level
Problem 9
In the electrochemical reaction of the conductivity sensor, which of the following
receives an electron from the cathode?
a.
b.
c.
d.
e.
f.
g.
h.
Na+
OHH2
H+
H2O
Cl2
Cle-
Problem 10
What TWO steps does this piece of code do just after adding DI water?
1.
2.
3.
4.
Records the current time
Checks if salinity is too low
Checks if deadtime is past
Pauses ½ second
a.
b.
c.
d.
e.
void loop() {
check_sensor();
// function to measure conductivity
t_since = millis() - t_last;
if(t_since>deadtime) {
if(analogS>UCL) {
add_DI();
// function that adds DI water
t_last=millis();
}
1 then 4
4 then 2
2 then 4
4 then 3
1 then 2
if(analogS<LCL) {
add_salty(); // function that adds salty
t_last=millis();
}
}
delay(500);
}
Problem 11
If the chamber below is completely filled with water, then the mass of water will be closest to . . .
(angles that appear to be right angles are right angles)
a.
b.
c.
d.
e.
f.
g.
1000 kg
2000 kg
3000 kg
4000 kg
5000 kg
6000 kg
7000 kg
2m
Problem 12
A mass of 1 gram of NaCl is dissolved in 1 cubic meter of DI water. The number of Cl- ions that will be
present in the solution is closest to . . .
a.
b.
c.
d.
e.
f.
g.
h.
0.028 ions
35.5 ions
58.5 ions
35,500,000 ions
8.482 (10)21 ions
1.696 (10)22 ions
1.029 (10)23 ions
8.482 (10)23 ions
Problem 13
A mass of 10 grams of NaCl is dissolved in 1,000 grams of DI water. The %wt of NaCl in this solution is
closest to . . .
a.
b.
c.
d.
e.
f.
g.
0.99%
1.00%
1.01%
1.10%
10%
11%
99%
Problem 14
(5 points) Beth wants to add enough salt to 3 gallons of DI water to achieve a % weight of 3.5%,
roughly the salinity of ocean water. The number of pounds she should add is closest to …
a. 0.1 lb
b. 0.2 lb
c. 0.3 lb
d. 0.4 lb
e. 0.5 lb
f. 0.6 lb
g. 0.7 lb
h. 0.8 lb
i. 0.9 lb
Problem 15
(5 points) An Engineering 121 student is inspired to purchase a real fish tank. She selects a tank
that holds 2300 cubic inches of DI water. How many pounds of salt should she add if she wants
the salt concentration in the tank to be 0.08%?
a. 0.06 lb
b. 1.4 lb
c. 2.3 lb
d. 2.7 lb
e. 3.5 lb
f. 4.8 lb
g. 6.1 lb
h. 9.7 lb
Problem 16
(5 points) When hooking up the conductivity sensor to the Arduino as performed in class, the
value you get when you perform the analog read at the analog pin is 430. This means that the
voltage across the 10 kΩ resistor must be closest to …
a. 0.0 V
b. 0.1 V
c. 0.5 V
digital output = 5V when HIGH
d. 1.15 V
(set high periodically to measure conductivity)
e. 1.6 V
f. 2.1 V
g. 2.9 V
h. 4.5 V
i. 5.0 V
analog input
(measures voltage across 10kΩ resistor)
10 kΩ
Problem 17
(5 points) Your professor has asked you to place the word “ENGINEERING” on the bottom row of
the LCD panel, in the lower right corner. (The last letter of the word, which is “G”, will end up in
Row 3, Column 19.) Which of the following sets of commands will work?
a.
b.
c.
d.
e.
f.
g.
h.
Serial.write(188); Serial.write(“ENGINEERING”);
Serial.print(188); Serial.print(“ENGINEERING”);
Serial.write(196); Serial.write(“ENGINEERING”);
Serial.print(196); Serial.print(“ENGINEERING”);
Serial.write(197); Serial.write(“ENGINEERING”);
Serial.print(197); Serial.print(“ENGINEERING”);
Serial.write(198); Serial.write(“ENGINEERING”);
Serial.print(198); Serial.print(“ENGINEERING”);
0
0
1
2
3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Problem 18
(5 points) A constant current passes through a conductivity sensor. If 2.0 (10)20 H2 molecules are
formed in a 5-minute period, then, the current passing through the sensor is closest to …
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
58 mA
214 mA
573 mA
1.28 A
1.57 A
1.83 A
2.45 A
3.69 A
Problem 19
(5 points) If a current of 20 mA passes through the electrodes of your conductivity sensor over a 5 minute
period, then the number of Cl2(g) molecules generated is closest to:
a.
b.
c.
d.
e.
f.
g.
h.
6.32x1019
3.94x1019
6.19x1019
1.87x1019
5.03x1019
1.77x1019
7.58x1019
6.58x1019
molecules
molecules
molecules
molecules
molecules
molecules
molecules
molecules
Problem 20
(5 points) What electrical current would be required to convert one mole of Chlorine ions to
Chlorine gas and electrons over a 10 hour time period?
a.
b.
c.
d.
e.
f.
g.
h.
2.68
4.20
5.57
5.29
8.97
3.86
4.37
6.64
A
A
A
A
A
A
A
A
Problem 21
(5 points) You are mixing a batch of dry concrete. So far you have 50 pounds of a mixture that is
20.0% cement, 35.0% sand, and 45.0% gravel. You want to create a mixture that is 17.0% cement,
29.8% sand, and 53.2% gravel. The amount of dry gravel that you need to add to the mixture is
closest to:
a.
b.
c.
d.
e.
f.
g.
h.
6.8
3.1
7.3
5.7
8.8
1.4
1.1
9.1
lb
lb
lb
lb
lb
lb
lb
lb
Problem 22
(5 points) You are making play dough by mixing corn flour (dry ingredient) and hair conditioner
(wet ingredient). One batch was too wet (you used 75% conditioner and 25% corn flour), and the
other batch is too dry (you used 25% conditioner and 75% corn flour). The amount of the wet
batch do you need to add to 2 pounds of the dry batch if you want play dough that is 33%
conditioner, and 67% corn flour is closest to:
a.
b.
c.
d.
e.
f.
g.
h.
1.22
0.59
2.67
0.14
1.82
2.03
0.38
0.97
lb
lb
lb
lb
lb
lb
lb
lb
Problem 23
(5 points) Ten liters of solution A with an unknown concentration of NaCl in water is mixed with
1.5 liters of solution B (0.2%wt NaCl). If the resulting mixture has a concentration of 0.8%wt NaCl,
the %wt NaCl in solution A is closest to…
(Assume that the densities of the salt solutions are 1kg/L)
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
0.71%
0.97%
1.66%
1.17%
1.24%
0.89%
1.87%
1.52%
1.05%
0.94%
Problem 24
(5 points) The first step of manufacturing asphalt shingles is to impregnate a fiberglass felt with a mixture of
asphalt cement and aggregate. At the end of this step, the shingles are 23% fiberglass by weight. The next
step is to apply an additional layer of aggregate to one side of the shingles. At the end of this step, the
shingles must be 15% fiberglass, 46% aggregate, and 39% asphalt cement by weight. At the end of the first
manufacturing step, the weight percentage of asphalt cement in the shingles is closest to:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
47.8%
50.2%
52.6%
55%
57.4%
59.8%
62.2%
64.6%
67%
69.4%
Problem 25
(5 points) One ENGR121 team has determined the best calibration equation for their conductivity sensor in
the range between 0.05% and 0.15% salt water is the one given below (this equation yields a fraction, not a
percentage). This team has also determined that the flowrate from their salty water tank into their control
volume when the salty valve is opened is 0.12 L/min. The team begins to run their system, but only puts 32
grams of an unknown concentration of salt water in the control volume, which only fills it to about halfway
to the drain port height. The analogRead value read by the Arduino with this charge of water is 482. If the
team has 1% salt water in the salty water tank, then the amount of time the team would want to open the
salty water valve to bring the salt concentration to a target value of 0.105% would be closest to:
Calibration Equation:
a. 0.24 seconds
𝑎𝑛𝑎𝑙𝑜𝑔𝑅𝑒𝑎𝑑 𝑣𝑎𝑙𝑢𝑒 − 432
𝑠𝑎𝑙𝑖𝑛𝑖𝑡𝑦𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛 =
b. 0.34 seconds
72500
c. 0.44 seconds
Hints:
d. 0.54 seconds
• Given the initial water level in the system, water is unlikely
to drain in the process of correcting the system’s salinity.
e. 0.64 seconds
• You may assume the density of all concentrations of salt
f. 0.74 seconds
water to be the same as that of DI water.
g. 0.84 seconds
• You do not need to factor in a “gain” term.
h. 0.94 seconds
i. 1.04 seconds
j. 1.14 seconds
Problem 26
(5 points) Alligator hides may be tanned using a mixture of water, salt, and a tanning agent called Lutan F.
One expert alligator hunter recommends a mixture that is 7.2% salt and 1.12% Lutan F by weight for tanning
Alligator hides. You would like to use this recipe.
Because you had been preparing for a different process that you ultimately decided not to do, you already
have 20 gallons of 9% salt water. You also have 2 gallons of an 11% mixture of Lutan F and water.
You would like to make the biggest batch that you can of the desired recipe using only the two prepared
mixtures you already have, and adding additional water if necessary. (You are going to estimate the density
of all of the mixtures using the density of pure water.) The biggest batch that you can make of the desired
recipe is closest to:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
8.8 gallons
10.6 gallons
12.4 gallons
14.2 gallons
16 gallons
17.8 gallons
19.6 gallons
21.4 gallons
23.2 gallons
25 gallons
1 coulomb = 6.24(10)18 electrons
Avogadro’s Number: 6.022(10)23
Density of water at 4°C (maximum density) = 1 g/mL = 1g/cm3 = 1000 kg/m3 = 8.33 lbs/gal
1 L = 0.001 m3 = 1.0567 quarts = 0.264 gal = 61.02 in3
1 pound = 16 ounces = 453.592 grams
Conductivity Sensor Reactions:
2𝐶𝑙 −𝑎𝑞
𝐶𝑙2 (𝑔) + 2𝑒 − and
1 gal = 0.1337 ft3 = 3.785 L
1 inch = 25.4 mm
2𝐻2 0(𝑙) + 2𝑒 −
1 foot = 12 inch
−
𝐻2 (𝑔) + 2𝑂𝐻(𝑎𝑞)
Atomic Weights:
Na = 23.0 g/mol, Cl = 35.5 g/mol, C = 12.0 g/mol, H = 1.0 g/mol, O = 16.0 g/mol
Volume of Cylinder =
𝜋 ∙ 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 2
4
∙ ℎ𝑒𝑖𝑔ℎ𝑡
/*****************************************************************************/
/* A partial listing of commands recognized by the LCD is provided below.
*/
/* See the data sheet for the LCD on the Parallax web site for more details. */
/* Serial.write(8) - move cursor one space left
*/
/* Serial.write(9) - move cursor one space right
*/
/* Serial.write(10) - move cursor down one line
*/
/* Serial.write(12) - clear screen and move cursor to top left
*/
/* Serial.write(13) - carriage return (will wrap if on last line)
*/
/* Serial.write(17) - turn backlight on
*/
/* Serial.write(18) - turn backlight off
*/
/* Serial.write(21) - turn display off
*/
/* Serial.write(22) - turn display on, cursor off, no blink
*/
/* Serial.write(23) - turn display on, cursor off, character blink
*/
/* Serial.write(24) - turn display on, cursor on, no blink (default)
*/
/* Serial.write(25) - turn display on, cursor on, character blink
*/
/* Serial.write(128) moves the cursor to row 0 and position 0
*/
/* row and position commands are shown below for all 80 character positions */
/*
ROW 0:
128=(0,0) 129=(0,1) 130=(0,2) 131=(0,3) 132=(0,4)
*/
/*
133=(0,5) 134=(0,6) 135=(0,7) 136=(0,8) 137=(0,9)
*/
/*
138=(0,10) 139=(0,11) 140=(0,12) 141=(0,13) 142=(0,14)
*/
/*
143=(0,15) 144=(0,16) 145=(0,17) 146=(0,18) 147=(0,19)
*/
/*
ROW 1:
148=(1,0) 149=(1,1) 150=(1,2) 151=(1,3) 152=(1,4)
*/
/*
153=(1,5) 154=(1,6) 155=(1,7) 156=(1,8) 157=(1,9)
*/
/*
158=(1,10) 159=(1,11) 160=(1,12) 161=(1,13) 162=(1,14)
*/
/*
163=(1,15) 164=(1,16) 165=(1,17) 166=(1,18) 167=(1,19)
*/
/*
ROW 2:
168=(2,0) 169=(2,1) 170=(2,2) 171=(2,3) 172=(2,4)
*/
/*
173=(2,5) 174=(2,6) 175=(2,7) 176=(2,8) 177=(2,9)
*/
/*
178=(2,10) 179=(2,11) 180=(2,12) 181=(2,13) 182=(2,14)
*/
/*
183=(2,15) 184=(2,16) 185=(2,17) 186=(2,18) 187=(2,19)
*/
/*
ROW 3:
188=(3,0) 189=(3,1) 190=(3,2) 191=(3,3) 192=(3,4)
*/
/*
193=(3,5) 194=(3,6) 195=(3,7) 196=(3,8) 197=(3,9)
*/
/*
198=(3,10) 199=(3,11) 200=(3,12) 201=(3,13) 202=(3,14)
*/
/*
203=(3,15) 204=(3,16) 205=(3,17) 206=(3,18) 207=(3,19)
*/
/*****************************************************************************/